The biocompatibility of porous vs non-porous bone cements: a new methodological approach.

Composite cements have been shown to be biocompatible, bioactive, with good mechanical properties and capability to bind to the bone. Despite these interesting characteristic, in vivo studies on animal models are still incomplete and ultrastructural data are lacking. The acquisition of new ultrastructural data is hampered by uncertainties in the methods of preparation of histological samples due to the use of resins that melt methacrylate present in bone cement composition. A new porous acrylic cement composed of polymethyl-metacrylate (PMMA) and β-tricalcium-phosphate (p-TCP) was developed and tested on an animal model. The cement was implanted in femurs of 8 New Zealand White rabbits, which were observed for 8 weeks before their sacrifice. Histological samples were prepared with an infiltration process of LR white resin and then the specimens were studied by X-rays, histology and scanning electron microscopy (SEM). As a control, an acrylic standard cement, commonly used in clinical procedures, was chosen. Radiographic ultrastructural and histological exams have allowed finding an excellent biocompatibility of the new porous cement. The high degree of osteointegration was demonstrated by growth of neo-created bone tissue inside the cement sample. Local or systemic toxicity signs were not detected. The present work shows that the proposed procedure for the evaluation of biocompatibility, based on the use of LR white resin allows to make a thorough and objective assessment of the biocompatibility of porous and non-porous bone cements.